The present invention relates to specific oxime alkyl sulfonate compounds, i.e. compounds containing the structural unit 
and to their use as photo-sensitive acid generator in chemically amplified photoresists, in printing plates, colour filters or image recording materials which are developable in alkaline medium, to their use as dissolution inhibitors in a corresponding positive photoresist, and to a process for the production of images using such resists, printing plates or image recording materials.
A chemically amplified photoresist will be understood as meaning a resist composition, the photosensitive component of which, when irradiated, generates only that amount of acid which is required to catalyse a chemical reaction of at least one acid-sensitive component of the resist, as a result of which the ultimate differences in solubility between irradiated and non-irradiated areas of the photoresist first develop.
Industrial paint formulations based on a large number of photosensitive oxime sulfonates and conventional acid-curable resins are disclosed in U.S. Pat. No. 4,540,598. These formulations are cured firstly with actinic light, especially with radiation in the range of 250 to 400 nanometers. The oxime sulfonates generate acid, so that a thermal cure in which the material also becomes insoluble in customary solvents is able to take place even at quite low temperatures. Nothing can be inferred about an imagewise exposure of corresponding resist films or about related problems as well as the image properties of the numerous formulations falling within the generic scope of the teaching of this patent specification. Oxime sulfonates, which are sparingly soluble in alkaline-aqueous developers, can be converted to the soluble form of the free acid by irradiation. Combined with a suitable film-forming resin, they can therefore be used as dissolution inhibitors for the production of positive resists.
Conventional positive photoresist compositions based on oxime sulfonates and alkali-soluble binders, typically cresol novolaks or hydroxymethacrylate/acrylic acid copolymers, are also known and are disclosed in EP-A-0 241 423. According to this reference, radiation of 200 to 600 nm can be used for exposing the resists. The shortcoming of these photo-resists is, however, that resolution and sensitivity are simultaneously never altogether satisfactory. This is particularly the case upon exposure to radiation in the range of the mercury i-line, which has a wavelength of 365 nanometers and is often used for the imagewise exposure of resist films, because mercury medium- and high-pressure lamps are inexpensive sources of radiation for producing radiation of these wavelengths with good intensity.
In the article xe2x80x9cPhotochemistry of Imino Sulfonate Compounds and Their Application to Chemically Amplified Resistsxe2x80x9d by Masamitsu Shirai and Masahiro Tsunooka; Journal of Photopolymer Science and Technology, Vol. 3(3), 1990, p. 301-304, there are also disclosed chemically amplified photoresist compositions based on oxime sulfonates as acid generator and poly(p-tert-butyloxycarbonyloxystyrene) as acid-sensitive component. The styrene component decomposes, catalysed by the acid generated by the acid generator upon exposure to irradiation to form poly(p-hydroxystyrene). This results in the exposed areas becoming soluble in alkaline developers so that positive images can be obtained with such developers. The described oxime sulfonates have an absorption maximum of about 250 nanometers in the UV/VIS spectrum, but have only low absorption for radiation in the wavelength of 313 nanometers and higher. Thus only a low sensitivity of the compositions to 313 nanometers radiation was found.
GB-A 2 306 958 describes the use of oxime sulfonates as photosensitive acid generators which are in particular suitable for use with light having a wavelength higher than 390 nm. However, the resolution and sensitivity of the resist formulations obtained with these initiators is not satisfactory.
Accordingly, there is still a need for reactive nonionic latent acid generators which are thermally and chemically stable and which, after being activated by light, in particular by radiation having the wavelength of the mercury i-line (365 nm), can be used as catalysts for different acid-catalysed reactions, such as polycondensation reactions, acid-catalysed depolymerisation reactions, acid-catalysed electrophilic substitution reactions or the acid-catalysed removal of protective groups. There is, in particular, a need for acid generators which can be activated with light and with which systems of higher sensivity and better resolution are obtained, having improved properties such as the form of the resist profiles and steepness of the side walls. Furthermore, there is a need for compounds which are converted to an acid when exposed to light and which can act as dissolution inhibitors in resist formulations.
U.S. Pat. No. 5,627,011 discloses the use of oxime sulfonate compounds in high-resolution i-line photoresists of high sensitivity. However, this publication only mentions oxime sulfonate compounds which can generate aromatic sulfonic acids. Surprisingly, it has now been found that resists of good sensitivity, resolution and having excellent resist profiles are obtained when an alkyl sulfonic acid is photochemically generated.
U.S. Pat. No. 4,451,286 discloses, among other oximes which do not contain any sulfonic acid groups, the compounds methylsulfonyloxyiminobenzylcyanide, methylsulfonyloxyiminonaphthylcyanide and methylsulfonyloxyimino-3-thiophenylcyanide in combination with chloroacetanilide compounds as plant protection agents.
This invention provides photoresist compositions having excellent resolution coupled with excellent sensitivity. These properties are observed especially when the resist compositions are exposed to radiation in the range of the mercury i-line which has a wavelength of about 365 nanometers.
Surprisingly, excellent resolution and outstanding sensitivity are achieved by using oxime alkyl sulfonates of formula I below which have been specially chosen with respect to the chromophoric part of the molecule as photoacid generators in chemically amplified photo-resist compositions which are developable in aqueous-alkaline media. This applies both to corresponding negative as well as to positive photoresists containing an acid-sensitive component that undergoes an acid-catalysed chemical reaction which changes the solubility of the compositions in aqueous-alkaline developers.
Accordingly, this invention relates to compositions which can be actived by light, comprising
a) at least one compound which may be crosslinked by the action of an acid and/or
b) at least one compound which changes its solubility under the action of an acid, and
c) as photoinitiator at least one compound of formula 1 
R0 is either an R1xe2x80x94X group or R2;
X is a direct bond or an oxygen atom;
R1 is hydrogen, C1-C4alkyl which is unsubstituted or substituted by phenyl, OH or C1-C4-alkoxy or which may be interrupted by an xe2x80x94O-atom, or R1 is a phenyl group which is unsubstituted or substituted by a substituent selected from the group consisting of chloro, bromo,
C1-C4alkyl and C1-C4alkyloxy;
R2 is hydrogen or C1-C4alkyl; and
R3 is straight-chain or branched C1-C12alkyl, which is unsubstituted or substituted by one or more than one halogen atoms, or is phenyl-C1-C2alkyl or campheryl, which composition can contain other photoinitiators, sensitisers and/or additives besides component c). The invention also relates to the use of compounds of formula 1 as photosensitive acid generators in a photoresist sensitive to radiation in a wavelength of up to 390 nanometers.
The invention further relates to chemically amplified photoresists which are developable in alkaline medium and which are sensitive to radiation in the range from 340 to 390 nanometers, which resists are based on oxime alkyl sulfonates as photosensitive acid generator and contain a compound of formula 1 as defined above as oxime alkyl sulfonate.
According to this invention it is also possible to use mixtures of isomeric forms (cis-trans isomers, also known as E/Z- or syn/anti-isomers) of the oxime alkyl sulfonates of formula 1.
It is the object of this invention to provide, in particular, photoresists comprising compounds of formula 1. These resists encompass chemically amplified, positive photoresists which are developable in alkaline medium and are sensitive to radiation in the range from 340 to 390 nanometers, which resists are based on oxime alkyl sulfonates as photosensitive acid generator and contain a compound of the above formula 1 as oxime alkyl sulfonate, wherein X, R, R0, R1, R2 and R3 also have the meanings assigned to them above.
Another embodiment of the invention relates to chemically amplified, negative photoresists which are developable in alkaline medium and are sensitive to radiation in the range from 340 to 390 nanometers, which resists are based on oxime alkyl sulfonates as photosensitive acid generator and contain a compound of formula 1 defined above as oxime alkyl sulfonate, wherein R, R0, R3 and X have the meanings assigned to them above, and R1 is hydrogen, C1-C4alkyl or a phenyl group which is unsubstituted or substituted by a substituent selected from the group consisting of chloro, bromo, C1-C4alkyl and C1-C4alkyloxy, and R2 is hydrogen or C1-C4alkyl.
Both embodiments of the inventive photoresists are readily able to resolve structural units having dimensions in the submicron range, typically structures having dimensions down to 0.3 xcexcm, the radiation used being in the range of c. 340 to 390 nanometersm. The resist structures remaining on the substrate after development exhibit in addition very good steepness of the side walls. The resists further have superior lithographic sensitivity to the given radiation. This feature was especially unexpected, as the oxime alkyl sulfonates chosen as acid generators absorb radiation of this wavelength only to an extremely low extent. The novel photoresists therefore match deep UV resists as regards lithographic properties, but have the advantage that they work with radiation of the near UV range with which it is possible to effect exposure technically very much easier.
The photoresists preferably comprise compounds of formula 1, wherein R is 
X is a direct bond or an oxygen atom; R1 is C1-C4alkyl or phenyl; R3 is straight-chain or branched C1-C12alkyl which is unsubstituted or substituted by one or more than one halogen atom.
This invention also relates to the use of compounds of formula 1 as photoinitiators for compounds which can be crosslinked by the action of an acid or/and as dissolution inhibitors for compounds which change their solubility under the action of an acid, where the irradiation is carried out, for example, imagewise.
Some of the compounds of formula 1 are novel. Accordingly, this invention also relates to compounds of formula 1a 
R0 is either a R1xe2x80x94X group or R2;
X is a direct bond, an oxygen atom or a sulfur atom;
R1 is hydrogen, C1-C4alkyl or a phenyl group which is unsubstituted or substituted by a substituent selected from the group consisting of chloro, bromo, C1-C4alkyl and C1-C4alkyloxy;
R2 is hydrogen or C1-C4alkyl; and
R3 is straight-chain or branched C1-C12alkyl which is unsubstituted or substituted by one or more than one halogen atom,
with the proviso that, if R3 is methyl, R is not naphthyl, phenyl or 3-thienyl.
R1 and R2 defined as C1-C4alkyl can be each independently of the other methyl, ethyl, n-propyl, i-propyl, n-butyl-, i-butyl, sec-butyl or tert-butyl.
R3 defined as straight-chain or branched C1-C12alkyl can typically be methyl, ethyl, n-propyl, i-propyl, n-butyl-, i-butyl, sec-butyl, tert-butyl, n-octyl or n-dodecyl. If C1-C12alkyl R3 is substituted by halogen, then it is, for example, chloromethyl, trichloromethyl, 3-chloropropyl, tri-fluoromethyl or completely fluorinated radicals derived from the cited alkyl radicals. Substituted by one or more than one halogen means, for example, substituted by one to three or two halogens, preferably by one to three halogens.
Preferred photoresists, printing plates, colour filters or image recording systems according to this invention comprise oxime alkyl sulfonate compounds of formula 
wherein
X is a direct bond or an oxygen atom, R1 is hydrogen, phenyl or C1-C4alkyl, R2 is hydrogen or C1-C4alkyl, and R3 is straight-chain or branched C1-C8alkyl, trichloromethyl or trifluoro-methyl.
Of these, those photoresists are particularly preferred which comprise an oxime sulfonate compound, wherein X is a direct bond or an oxygen atom, R1 is a C1-C4alkyl radical, preferably methyl or ethyl, or phenyl, and R2 is hydrogen or methyl. Very particularly preferably, X is a direct bond or oxygen, R1 is methyl, R2 is a hydrogen atom or methyl, and R3 is a CH3, CCl3 or CF3 group.
Also preferred are photoresists based on compounds of formula 1 as acid generator, wherein R is 
R0 is hydrogen, and R3 is straight-chain or branched C1-C12-alkyl which is unsubstituted or substituted by one or more than one halogen atom.
Preferred compounds are those of formula 1a, wherein X is a direct bond or an oxygen atom; R1 is hydrogen or C1-C4alkyl, and R3 is straight-chain or branched C1-C8alkyl which is unsubstituted or substituted by one or more than one halogen atom, or CCl3 or CF3.
Particularly interesting compounds are xcex1-(methylsulfonyloxyimino)-4-methoxybenzylcyanide, xcex1-(methylsulfonyloxyimino)-3-meth-oxybenzylcyanide, xcex1-(methylsutfonyloxyimino)-4-methylbenzylcyanide, xcex1-(methylsulfonyl-oxyimino)-3,4-dimethylbenzylcyanide, xcex1-(methylsutfonyloxyimino)thiophene-3-acetonitrile , xcex1-(methylsulfonyloxyimino)thiophene-2-acetonitrile, xcex1-(isopropylsulfonyloxyimino)thiophene-2-acetonitrile, xcex1-(butylsulfonyloxyimino)thiophene-2-acetonitrile, xcex1-(octylsulfonyloxyimino)thio-phene-2-acetonitrile, xcex1-(dodecylsulfonyloxyimino)thiophene-2-acetonitrile, xcex1-(dodecylsulfonyloxyimino)thioph ne-2-acetonitrile, xcex1-(3-chloropropylsulfonyloxyimino)thiophene-2-acetonitrile, xcex1-(trifluorometyhlsulfonyloxyimino)thiophene-2-acetonitrile, xcex1-(octylsulfonyloxyimino)-4-methoxybenzylcyanide, xcex1-(3-chloropropylsulfonyloxyimino)-4-methoxybenzylcyanide. Mixtures of isomeric forms (cis/trans isomeres, also called E/Z- or syn/anti-isomers) are also novel.
The novel oxime alkyl sulfonates of formula 1 or 1a can be prepared by methods described in the literature, e.g. by reacting suitable free oximes of formula 2 with alkylsulfonic acid halides of formula 3 in the presence of a base such as triethylamine, or by reacting the salt of an oxime with an alkylsulfonic acid chloride. These methods have been published, inter alia, in EP-A 48615. 
The reaction is conveniently carried out in an inert organic solvent in the presence of a tertiary amine.
The sodium salts of oximes can be obtained, for example, by reacting the corresponding oxime with a sodium alcoholate in dimethylformamide (DMF).
Oxime alkylsulfonic acid derivatives containing a heterocyclic aromatic five-ring substituent can also be prepared by 1,3-dipolar cycloaddition of suitable alkylsulfonic acid derivatives, typically the esters of oximinomalodinitrile or oximinocyanoacetate, with a suitable 1,3-dipolar compound, such as nitrile oxide. Such a synthesis is described, inter alia, in J. Perrocheau, R. Carrxc3xa9, Bull. Soc. Chim. Belge 1994, 103, 9.
The oxime alkyl sulfonates can be obtained in the syn- (E, cis) or anti- (Z, trans) form or also as mixtures of the two conformers. According to this invention it is possible to use single conformers as well as any mixture of the two conformers.
The oximes (2) required for the reaction can be prepared in general analogy to known methods, for example by reacting compounds containing reactive methylene groups, such as benzylcyanide derivatives or phenylacetic acid derivates, with an alkyl nitrite, e.g. methyl nitrite or isoamyl nitrite, and a sodium alcoholate, e.g. sodium methanolate. Such reactions are described, inter alia, in xe2x80x9cThe systematic identification of organic compoundsxe2x80x9d, John Wiley and Sons, New York, 1980, p. 181, in xe2x80x9cDie Makromolekulare Chemiexe2x80x9d, 1967, 108, 170, or in xe2x80x9cOrganic Synthesisxe2x80x9d, 1979, 59, 95.
Oximes can also be obtained e.g. by reacting a corresponding carbonyl compound or thiocarbonyl compound with hydroxylamine. They can also be prepared by the nitrosation of hydroxyaromatics.
The preparation of alkylsulfonic acid halides (3) is known to the skilled person and is described, for example, in the standard chemistry textbooks.
In photocurable compositions, oximesulfonic acid esters act as latent curing catalysts: when irradiated with light they generate acid which catalyses the crosslinking reaction. In addition, the acid generated by the radiation can, for example, catalyse the removal of suitable acid-sensitive protective groups from a polymer structure, or the cleavage of polymers containing acid-sensitive groups in the polymer backbone. Other applications are, for example, colour-change systems based on a change in the pH or in the solubility of, for example, a pigment protected by acid-sensitive protective groups. Finally, oximesulfonic acid esters that are sparingly soluble in an aqueous-alkaline developer can be rendered soluble in the developer by means of light-induced conversion into the free acid, with the result that they can be used as dissolution inhibitors in combination with suitable film-forming resins. Resins that can be crosslinked by acid catalysis are, for example, mixtures of polyfunctional alcohols or hydroxy-group-containing acrylic and polyester resins, or partially hydrolysed polyvinyl acetals or polyvinyl alcohols with polyfunctional acetal derivatives. Under certain conditions, for example the acid-catalysed self-condensation of acetal-functionalised resins is also possible. In addition, oximesulfonates can be used e.g. as hardeners which can be activated by light for siloxane group-containing resins. Those resins can, for example, either undergo self-condensation by means of acid-catalysed hydrolysis or be crosslinked with a second component of the resin, such as a polyfunctional alcohol, a hydroxy-group-containing acrylic or polyester resin, a partially hydrolysed polyvinyl acetal or a polyvinyl alcohol. This type of polycondensation of polysiloxanes is described, for example, in J. J. Lebrun, H. Pode, Comprehensive Polymer Science, Volume 5, page 593, Pergamon Press, Oxford, 1989.
As already mentioned above, the difference in solubility between irradiated and non-irradiated sections that occurs as a result of the acid-catalysed reaction of the resist material during or after irradiation of the resist may be of two types depending on which further constituents are present in the resist. If the compositions according to the invention comprise components that increase the solubility of the composition in the developer, the resist is positive. If, on the other hand, these components reduce the solubility of the composition, the resist is negative.
Acid-sensitive components that produce a negative resist characteristic are in particular compounds that, when catalysed by acid (the acid formed during irradiation of the compound of formula 1), are capable of undergoing a crosslinking reaction with themselves or with one or more further components of the composition. Compounds of this type are, for example, the known acid-curable resins, such as, for example, acrylic, polyester, alkyd, melamine, urea, epoxy and phenolic resins, or mixtures thereof. Amino resins, phenolic resins and epoxy resins are very suitable. Acid-curable resins of this type are generally known and are described, for example, in Ullmann""s Encyclopxc3xa4die der technischen Chemie, 4th Edition, Vol. 15 (1978), p. 613-628. They should generally be present in a concentration of 2 to 40% by weight, preferably of 5 to 30% by weight, based on the total solids content of the negative composition.
Very particularly preferred as acid-curable resins are amino resins, such as non-etherified or etherified melamine, urea, guanidine or biuret resins, preferably methylated melamine resins or butylated melamine resins, corresponding glycolurils and urones. Resins are understood in this context to be the customary technical mixtures, which usually also comprise oligomers, as well as pure and high purity compounds. N-methoxymethyl melamine (formula 7) and tetramethoxymethyl glucoril (formula 8) and N,Nxe2x80x2-dimethoxymethylurone (formula 9) are the acid-curable resins given the greatest preference 
The concentration of the compound of formula I in negative resists is typically from 0.1 to 30% by weight, preferably up to 20% by weight, likewise based on the total solids content of the compositions. From 1 to 15% by weight is very particularly preferred.
Where appropriate, the negative compositions may additionally comprise a film-forming polymeric binder. This binder is preferably an alkali-soluble phenolic resin. Well suited for that purpose are, for example, novolaks, derived from an aldehyde, typically acetaldehyde or furfuraldehyde, but especially from formaldehyde, and a phenol, for example unsubstituted phenol, mono- or di-chlorosubstituted phenol, such as p-chlorophenol, phenol mono- or di-substituted by C1-C9alkyl, such as o-, m- or p-cresol, the various xylenols, p-tert-butyl-phenol, p-nonylphenol, p-phenylphenol, resorcinol, bis(4-hydroxyphenyl)methane or 2,2-bis(4-hydroxyphenyl)propane. Also suitable are homo- and copolymers based on ethylenically unsaturated phenols, for example homopolymers of vinyl- and 1-propenyl-substituted phenols, such as p-vinylphenol or p-(1-propenyl)phenol, or copolymers of these phenols with one or more than one ethylenically unsaturated material, for example styrenes. The amount of binder should generally be from 30 to 95% by weight or, preferably, from 40 to 80% by weight.
The invention thus includes, as a special embodiment, negative photoresists which are developable in alkaline medium for a working radiation of a wavelength of more than 390 nanometers, comprising an oxime alkyl sulfonate of formula 1 as described above, an alkali-soluble phenolic resin as binder and a component that, when catalysed by an acid, undergoes a crosslinking reaction with itself and/or with the binder.
A particularly preferred form of that negative resist comprises from 1 to 15% by weight of oxime alkyl sulfonate, from 40 to 99% by weight of a phenolic resin as binder, for example one of those mentioned above, and from 0.5 to 30% by weight of a melamine resin as crosslinking agent, the percentages relating to the solids content of the composition. Using novolak or, in particular, polyvinyl phenol as binder gives a negative resist having especially good properties.
It is preferred to use a negative resist comprising N-methoxymethyl melamine or tetramethoxymethyl glucoril and N,Nxe2x80x2-dimethoxymethylurone in high purity or technical form as amino resin.
Oximesulfonates can also be used as acid generators which can be photochemically activated for the acid-catalysed crosslinking of, for example, poly(glycidyl)methacrylates in negative resist systems. Such crosslinking reactions are described, inter alia, by Chae et al. in Pollimo 1993, 17(3), 292.
Monomeric or polymeric compounds that are alkali-insoluble but are cleaved in the presence of acid, or are capable of being rearranged intramolecularly, in such a manner that reaction products remain that are soluble in a customary alkaline developer and/or that cause an otherwise alkali-insoluble and acid-resistant additional binder to become soluble in the developer, also produce a positive characteristic in novel photoresist compositions. Substances of that type are referred to hereinafter as dissolution inhibitors.
The invention therefore includes, as a further special embodiment, positive photoresists developable in alkaline medium for a working radiation of a wavelength of 340 to 390 nanometers, comprising a compound of formula 1, and at least one compound that substantially prevents the composition from dissolving in an alkaline developer, but that can be cleaved in the presence of an acid in such a manner that reaction products remain that are soluble in the developer and/or that cause an acid-resistant additional binder that would otherwise be virtually insoluble in the developer to dissolve in the developer.
There may be used as dissolution inhibitors monomeric and polymeric organic compounds having functional groups that would be soluble per se in an alkaline medium, for example aromatic hydroxyl groups, carboxylic acid groups, secondary amino groups and keto or aldehyde groups, but that have been chemically so altered by reaction with a suitable compound that they are insoluble in aqueous alkali, the protective groups formed in the mentioned reaction being capable of being cleaved again by acid catalysis in such a manner that the functional groups are recovered in their original form.
For the protection of hydroxyl groups, carboxylic acid groups or secondary amino groups there are suitable, for example, dihydrofuran or 3,4-dihydropyran and the derivatives thereof, benzyl halides, alkyl halides, haloacetic acid, haloacetates, chlorocarbonates, alkylsulfonyl halides, aromatic sulfonyl halides, dialkyl dicarbonates or trialkylsilyl halides, it being possible for the reactions to be carried out in known manner. Customary conversion into ketals and acetals is suitable for protecting keto and aldehyde groups. Such chemically amplified positive resist systems are described, inter alia, in E. Reichmanis, F. M. Houlihan, O. Nalamasu, T. X. Neenan, Chem. Mater. 1991, 3, 394; or in C. G. Willson, xe2x80x9cIntroduction to Microlithography, 2nd. Ed.; L. S. Thompson, C. G. Willson, M. J. Bowden, Eds., Amer. Chem. Soc., Washington D.C., 1994, p. 139.
Compounds carrying blocked aromatic hydroxyl groups are particularly preferred, which compounds may likewise be monomers as well as polymers. The aromatic monomers preferably contain one or more than one aromatic nucleus, preferably 2 to 6 aromatic nuclei, containing 6 to 14, preferably 6, ring carbon atoms. In addition to containing the blocked hydroxyl groups, the aromatic nuclei may of course contain further substituents, preferably C1-C4alkyl, C1-C4alkoxy or halogen. Particularly preferred monomeric dissolution inhibitors are bisphenyl types, i.e. compounds of formula 
wherein each Y is an acid-sensitive group, such as a phenolic hydroxyl group, which is protected by a suitable acid-sensitive radical such as the ether, carbonate, silyl, tetrahydropyranyl or tetrahydrofuranyl groups (se e.g. EP-A 475903), and Z is either a direct single bond or may be one of the following groups: xe2x80x94Sxe2x80x94; xe2x80x94Oxe2x80x94; xe2x80x94SOxe2x80x94; xe2x80x94SO2xe2x80x94; xe2x80x94COxe2x80x94; xe2x80x94C(Ra)(Rb)xe2x80x94, where Ra may be hydrogen, methyl or aryl, and Rb may be hydrogen or methyl. Particularly preferred divalent radicals xe2x80x94C(Ra)(Rb)xe2x80x94 are xe2x80x94CH2xe2x80x94; xe2x80x94C(CH3)2xe2x80x94 and C(CH3)(Ph)xe2x80x94. The preferred polymeric dissolution inhibitors are derived from customary phenolic resins, typically from polyvinyl phenols, the hydroxyl groups of which are also blocked in a manner consistent with the above description. Dissolution inhibitors carrying protective groups of the indicated kind are known in the art. Inhibitors carrying carbonate groups are described, inter alia, by Dennis R. McKean, Scott A. McDonald, Nicholas J. Clecak and C. Grant Willson in xe2x80x9cNovolac based deep-UV resistsxe2x80x9d, SPIE Vol. 920 Advances in Resist Technology and Processing V (1988), p. 60-63, or by Masamitsu Shirai and Masahiro Tsunooka in xe2x80x9cPhotochemistry of Imino Sulfonate Compounds and their Application to Chemically Amplified Resistsxe2x80x9d, Journal of Photopolymer Science and Technology, Vol. 3(3), 1990, p. 301-304. They can be prepared by standard known methods, for example as described by J. M. J. Frechet, E. Eichler, H. Ito and C. G. Willson, Polymer 24 (1983), p. 995. Dissolution inhibitors carrying trialkylsilyloxy or tert-butyloxy groups are disclosed in EP-A-0 329 610, inhibitors carrying protective groups of the tetrahydrofuranyl and tetrahydropyranyl type group are described, inter alia, by N. Hayashi, S. M. A. Hesp, T. Ueno, M. Toriumi, T. Iwayanagi and S. Nonogaki in Polym. Mat. Sci. Eng. 61 (1989), p. 417-421, and aromatic compounds carrying substituted tetrahydropyranyl groups are described in more detail in EP-A-0 475 903. The protective groups can be obtained in known manner by addition of 3,4-dihydropyrans or 3,4-dihydrofurans under acid conditions.
In positive resists of the mentioned type a film-forming polymeric dissolution inhibitor can either be the only binder in the photoresist or can be used in admixture with an acid-inert binder and, where appropriate, a monomeric dissolution inhibitor.
Examples of acid-inert binders are novolaks, especially those based on o-, m- or p-cresol and formaldehyde, also poly(p-hydroxystyrene), poly(p-hydroxy-xcex1-methylstyrene) and copolymers of p-hydroxystyrene, p-hydroxy-xcex1-methylstyrene and acetoxystyrene.
Examples of polymeric dissolution inhibitors are novolaks, especially those based on o-, m- or p-cresol and formaldehyde, poly(p-hydroxystyrene), poly(p-hydroxy-xcex1-methylstyrene), copolymers of p-hydroxystyrene or p-hydroxy-xcex1-methylstyrene and acetoxystyrene or acrylic acid and/or methacrylic acid and also (meth)acrylic acid esters, which are reacted in known manner with dihydrofuran, 3,4-dihydropyran, benzyl halides, alkyl halides, haloacetic acid, haloacetates, chlorocarbonates, alkylsulfonyl halides, aromatic sulfonyl halides, dialkyl dicarbonate or trialkylsilyl halides. Also suitable are polymers of p-(2-tetrahydropyranyl)oxy-styrene or p-(tert-butyloxycarbonyl)oxystyrene with (meth)acrylic acid, (meth)acrylates and/or p-acetoxystyrene and polymers of p-hydroxystyrene and/or p-(2-tetrahydropyranyl)-oxystyrene with 3-hydroxybenzyl (meth)acrylates, which can, if necessary, additionally be protected by reaction with one of the compounds listed above.
Particularly suitable are polymers that are transparent over a wavelength range from 180 to 1000 nm and which carry groups that, after acid-catalysed deprotecting, bring about a change in solubility, as well as hydrophobic and hydrophilic groups that increase the solubility of the acid generator and ensure aqueous-alkaline developability. Examples of such polymers are acrylates and methacrylates prepared by co- or ter-polymerisation from the corresponding monomers. The monomers may also carry organosilicon radicals in order, for example, to increase the resistance in the case of dry etching processes. Examples of monomers are: methyl (meth)acrylate, (meth)acrylic acid, tert-butyl (meth)acrylate, trimethylsilylmethyl (meth)acrylate, 3-oxocyclohexyl (meth)acrylate, tetrahydropyranyl (meth)acrylate, adamantyl (meth)acrylate, cyclohexyl (meth)acrylate, norbornyl (meth)acrylate.
The invention accordingly also relates to a chemically amplified positive resist comprising as photosensitive acid generator a compound of formula 1 as well as to a photoresist comprising polymers that are transparent up to the wavelength region of 180 nm.
A special embodiment of the positive resist according to the invention comprises from 75 to 99.5% by weight of a film-forming polymer that contains protective groups that can be removed by acid catalysis, and from 0.5 to 25% by weight of oxime alkyl sulfonates of formula 1, the percentages being based on the solids content of the compositions. In this context, preference is given to compositions comprising from 80 to 99% by weight of the mentioned polymer and from 1 to 20% by weight of oxime alkyl sulfonate.
Another embodiment is a positive resist comprising from 40 to 90% by weight of an acid-inert film-forming polymer as binder, from 5 to 40% by weight of a monomeric or polymeric compound having protective groups removable by acid catalysis, and from 0.5 to 25% by weight of oxime alkyl sulfonates of formula I, the percentages relating to the solids content of the compositions. Of those compositions, preference is given to those comprising from 50 to 85% by weight of acid-inert binder, from 10 to 30% by weight of monomeric or polymeric dissolution inhibitor and from 1 to 15% by weight of oxime alkyl sulfonates.
Oxime sulfonates can also be used as solubilisers which can be activated by light. In that case, the compounds are added to a film-forming material comprising substantially no components that polymerise with the oximesulfonate when heated or when irradiated with actinic radiation. However, the oximesulfonates reduce the speed at which the film-forming material dissolves in a suitable developer medium. This inhibiting effect can be cancelled by irradiating the mixture with actinic radiation, so that a positive image can be produced. Such an application is described, inter alia, in EP-A-241 423.
A further special embodiment of the invention is, finally, a positive resist comprising a compound of formula 1 and a binder that is virtually insoluble in an alkaline developer and that becomes soluble in the developer in the presence of the photolysis products of the compound of formula I. In this case the amount of the mentioned oximesulfonate compound is generally from 5 to 50% by weight, based on the solids content of the composition.
The use of the oxime alkyl sulfonates according to the invention in chemically amplified systems, which operates on the principle of the removal of a protective group from a polymer, generally produces a positive resist. Positive resists are preferred to negative resists in many applications, especially because of their greater resolution. There is, however, also interest in producing a negative image using the positive resist mechanism, in order to combine the advantages of the high degree of resolution of the positive resist with the properties of the negative resist. That can be achieved by introducing a so-called image-reversal step as described, for example, in EP-A-361 906. For that purpose, the image-wise irradiated resist material is treated, before the developing step, with e.g. a gaseous base, the acid that has been produced image-wise being neutralised. Subsequently, a second irradiation, over its whole area, and thermal aftertreatment are carried out and the negative image is then developed in the customary manner.
In addition to the cited components, it is also possible to add compounds which accelerate or amplify the acid formation to the negative as well as to the positive photoresist compositions containing the novel oxime alkyl sulfonate. Such acid amplifiers are described, inter alia, in K. Arimitsu et al., J. photopolym. Sci Technol. 1995, 8, pp. 43, K. Kudo et al., J. photopolym. Sci Technol. 1995, 8, pp. 45, or K. Ichimura et al. Chem. Lett. 1995, pp. 551.
In addition to the mentioned constituents, both the negative and the positive photoresist compositions may additionally comprise one or more of the additives customarily used in photoresists in the amounts familiar to a person skilled in the art, for example flow control agents, wetting agents, adhesives, thixotropic agents, colourants, pigments, fillers, dissolution accelerators and so on. However, substances which additionally sensitise the compositions for the working irradation in the range of the mercury i-line should not be added because this would normally result in a reduced resolution of the resist. Typical examples of sensitisers which can be used in the novel composition in addition to component c) are, in particular, aromatic carbonyl compounds such as benzophenone, xanthone, thioxanthone, anthraquinone and 3-acylcoumarine derivatives as well as 3-(aroyl-methylene)thiazolines, and also eosine, rhodamine and erythrosine colourants.
For certain purposes, resin mixtures having monomeric or oligomeric constituents containing polymerisable unsaturated groups are used. Such surface coatings can also be cured using the compounds of formula 1. In addition to component c), it is possible to use 1. radical polymerisation initiators or 2. photoinitiators. The former initiate the polymerisation of the unsaturated groups during heat treatment, the latter during UV radiation. Examples of additional photoinitiators for use in the inventive compositions are, for example, radical photoinitiators, typically those from the class of the benzophenones, acetophenone derivatives, such as xcex1-hydroxycycloalkylphenyl ketone, dialkoxyacetophenone, xcex1-hydroxy- or xcex1-aminoacetophenone, 4-aroyl-1,3-dioxolane, benzoin alkyl ethers and benzil ketals, monoacylphosphine oxides, bisacylphosphine oxides or titanocenes. Illustrative examples of particularly suitable additional photoinitiators are: 1-(4-dodecylbenzoyl)-1-hydroxy-1-methylethane, 1-(4-isopropylbenzoyl)-1-hydroxy-1-methyl-ethane, 1-benzoyl-1-hydroxy-1-methylethane, 1-[4(2-hydroxyethoxy)benzoy]-1-hydroxy-1-methylethan, 1-[4(acrylolyoxyethoxy)benzoyl]-1-hydroxy-1-methylethane, diphenyl ketone, phenyl-1-hydroxycyclohexyl ketone, (4-morpholinobenzoyl)-1-benzyl-1-dimethylaminopropane, 1-(3,4-dimethoxyphenyl)-2-benzyl-2-dimethylaminobutan-1-one, (4-methylthiobenzoyl)-1-methyl-1-morpholinoethane, benzil dimethyl ketal, bis(cyclopentadienyl)-bis(2,6-difluoro-3-pyrrylphenyl)titanium, trimethylbenzoyidiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethyl-pentyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-dipentoxyphenyl-phosphine oxide or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. Other suitable additional photoinitiators are to be found in U.S. Pat. No. 4,950,581, column 20, line 35 to column 21, line 35. Other examples are trihalomethyltriazine derivatives or hexaarylbisimidazolyl compounds.
Further examples of additional photoinitiators are, for example, also cationic photoinitiators, typically peroxide compounds, such as benzoylperoxide (other suitable peroxides are described in U.S. Pat. No. 4,950,581, column 19, lines 17-25), aromatic sulfonium salts or iodonium salts, such as those to be found, inter alia in U.S. Pat. 4,950,581, column 18, line 60 to column 19, line 10, or cyclopentadienyl-arene-iron(II)-complex salts, typically (xcex76-isopropylbenzol)(xcex75-cyclopentadienyl)-iron-II-hexafluorophosphate.
For application, the compositions must generally also comprise a solvent. Examples of suitable solvents are ethyl acetate, 3-methoxymethyl propionate, ethyl pyruvate, 2-heptanone, diethyl glycol dimethyl ether, cyclopentanone, cyclohexanone, xcex3-butyrolactone, ethyl methyl ketone, 2-ethoxyethanol, 2-ethoxyethyl acetate and, in particular, 1-methoxy-2-propyl acetate. The solvent may also be in the form a mixture, for example of two or more of the above-mentioned solvents. The choice of solvent and the concentration depend, for example, on the nature of the composition and on the coating method.
The solution is uniformly applied to a substrate by means of known coating methods, for example by spin-coating, immersion, knife coating, curtain coating techniques, brush application, spraying and reverse roller coating. It is also possible to apply the photosensitive layer to a temporary, flexible support and then to coat the final substrate by coating transfer (laminating).
The amount applied (coating thickness) and the nature of the substrate (coating substrat) are dependent on the desired field of application. The range of coating thicknesses can in principle include values from approximately 0.1 xcexcm to more than 100 xcexcm.
Possible areas of use of the composition according to the invention are as follows: use as photoresists for electronics, such as etching resists, electroplating resists or solder resists, the manufacture of integrated circuits or thin film transistor resist (TFT resist), the manufacture of printing plates, such as offset printing plates or screen printing templates, use in the etching of mouldings or in stereolithography techniques, use in colour filters or image recording materials and, preferably, use as microresist in the manufacture of integrated circuits. The coating substrates and processing conditions vary accordingly.
When using the compositions as microresists for integrated and large-scale integrated circuits, as preferred, the layer thicknesses are typically from 0.1 to 10 xcexcm, preferably from 0.5 to 5 xcexcm, most preferably from 0.5 to 1.5 xcexcm. When using the compositions in resists for e.g. ion implantation the coating thicknesses are typically from 0.1 to 10 xcexcm, preferably from 4 to 8 xcexcm. By choosing suitable substituents R1 and R2, the optical density of the resist can be adjusted such that in particular the large layer thicknesses are also satisfactorily cured.
The compositions according to the invention are also outstandingly suitable as coating compositions for substrates of all types, including wood, textiles, paper, ceramics, glass, plastics, such as polyesters, polyethylene terephthalate, polyolefins or cellulose acetate, especially in the form of films, but especially for coating metals, such as Ni, Fe, Zn, Mg, Co or especially Cu and Al, and also Si, silicon oxides or nitrides, to which an image is to be applied by means of image-wise irradiation.
After the coating operation, the solvent is generally removed by heating, resulting in a lay r of the photoresist on the substrate. The drying temperature must of course be lower than the temperature at which certain components of the resist might be thermally cured. Care must be taken in that respect especially in the case of negative photoresists. In general, drying temperatures should not exceed from 80 to 130xc2x0 C.
The resist coating is then irradiated image-wise. This irradiation in a predetermined pattern using actinic radiation includes both irradiation through a photomask containing a predetermined pattern, for example a diapositive, and irradiation using a laser beam that is moved over the surface of the coated substrate, for example under the control of a computer, and thus produces an image.
Suitable radiation sources are those which emit radiation of a wavelength of approximately from 180 to 390, for example from about 340 to 360 or, preferably, from 360 to 390, nanometers. Both point sources and planiform projectors (arrays of reflector lamps) are suitable. Examples are: carbon arc lamps, xenon arc lamps, medium pressure, high pressure and low pressure mercury lamps, optionally doped with metal halides (metal halide lamps), microwave-excited metal vapour lamps, excimer lamps, superactinic fluorescent tubes, fluorescent lamps, argon filament lamps, electronic flash lamps, photographic flood lights, electron beams and X-ray beams generated by means of synchrotrons or laser plasma. Particularly suitable are mercury vapour lamps, especially mercury medium- and high-pressure lamps, from whose radiation the emission lines at other wavelengths are filtered out, if required. This is the case in particular for short-wave radiation. The distance between the lamp and the substrate according to the invention to be irradiated can vary, for example, from 2 cm to 150 cm, according to the intended use and the type and/or strength of the lamp. A suitable laser-beam source is, for example, the argon-ion laser, which emits radiation at wavelengths of 364 and 388 nanometers. With that type of irradiation, it is not absolutely essential to use a photomask in contact with the photopolymeric coating; the controlled laser beam is capable of writing directly onto the coating. For that purpose the high sensitivity of the materials according to the invention is very advantageous, allowing high writing speeds at relatively low intensities. On irradiation, the oxime alkyl sulfonate in the composition in the irradiated sections of the surface coating decomposes to form sulfonic acids.
After the irradiation and, if necessary, thermal treatment, the unirradiated sites (in the case of positive resists) or the irradiated sites (in the case of negative resists) of the composition are removed in a manner known per se using a developer.
It is generally necessary to allow a certain period of time prior to the developing step in order to allow the acid-sensitive components of the resist composition to react. In order to accelerate that reaction and hence the development of a sufficient difference in solubility between the irradiated and unirradiated sections of the resist coating in the developer, the coating is preferably heated before being developed. The heating can also be carried out or begun during the irradiation. Temperatures from 60 to 150xc2x0 C. are preferably used. The period of time depends on the heating method and, if necessary, the optimum period can be determined easily by a person skilled in the art by means of a few routine experiments. It is generally from a few seconds to several minutes. For example, a period of from 10 to 300 seconds is very suitable when a hotplate is used and from 1 to 30 minutes when a convection oven is used.
The coating is then developed, the portions of the coating that, after irradiation, are more soluble in the developer being removed. If necessary, slight agitation of the workpiece, gentle brushing of the coating in the developer bath or spray developing can accelerate that process step. The aqueous-alkaline developers customary in resist technology may be used, for example, for the developing. Such developers comprise, for example, sodium or potassium hydroxide, the corresponding carbonates, acid carbonates, silicates or metasilicates, but preferably metal-free bases, such as ammonia or amines, for example ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyl diethylamine, alkanolamines, for example dimethyl ethanolamine, triethanolamine, quaternary ammonium hydroxides, for example tetramethylammonium hydroxide or tetraethyl ammonium hydroxide. The developer solutions are generally up to 0.5N, but are usually diluted in suitable manner before use. For example solutions having a normality of approximately 0.1 are well suited. The choice of developer depends on the nature of the photoresist, especially on the nature of the binder used or of the resulting photolysis products. The aqueous developer solutions may, if necessary, also comprise relatively small amounts of wetting agents and/or organic solvents. Typical organic solvents that can be added to the developer fluids are, for example, cyclohexanone, 2-ethoxyethanol, toluene, acetone, isopropanol and also mixtures of two or more of those solvents. A typical aqueous/organic developer system is based on butylcellosolve(copyright)/water.
Accordingly, this invention also relates to a process for the production of an image, which comprises coating a substrate with a composition according to this invention, irradiating the coating with radiation having a wavelength of 340 to 390 nanometers in a desired pattern and, after a heating period, removing the more soluble sections of the coating with an aqueous-alkaline developer.
In another of its aspects, this invention also relates to the use of the novel composition for the production of printing plates, colour filters, resist materials and image recording material, as well as to the use of componds of formula 1 or 1a as photosensitive acid generator sensitive to radiation at a wavelength of below 390 nm in the production of printing plates, colour filters, resist materials or image recording materials, or for image recording materials for holographic images.
It is known from EP-A-592 139 that oximesulfonates can be used as acid generators which can be activated by light in compositions that are suitable for the surface treatment and cleaning of glass, aluminium and steel surfaces. The use of these compounds in such organosilane systems results in compositions that have significantly better storage stability than those obtained when the free acid is used. Oximesulfonates can also be used to produce so-called xe2x80x9cprint-outxe2x80x9d images when the compound is used together with a colourant that changes colour when the pH changes, as described in Japanese Patent Application JP-A Hei 4 328 552 or in U.S. Pat. No. 5,237,059. Such colour-change systems can be used according to EP-A-199 672 also to monitor goods that are sensitive to heat or radiation.
In addition to a colour change, it is possible during the acid-catalysed deprotection of soluble pigment molecules for the pigment crystals to be precipitated; this can be used in the production of colour filters.
The compounds of formula 1 are normally added to the compositions which can be activated by light in an amount of 0.1 to 30% by weight, e.g. of 0.5 to 10% by weight, preferably of 1 to 5% by weight.
The following Examples illustrate the invention in more detail. As in the remainder of the description and in the patent claims, parts and percentages are by weight, unless otherwise stated. 